Declare the page language (WCAG 3.1.1)

The <html> element must carry a valid lang attribute.

Why it matters

Screen readers use the language to choose the right pronunciation and voice. Without it, English read in a Turkish voice (or vice versa) is barely intelligible.

How to fix it

Set lang on the root element to the page's primary language, and mark inline language changes with lang on the relevant element.

<!-- Passes -->
<html lang="en">

<!-- Inline change -->
<span lang="tr">Merhaba</span>

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Related guides

Fix low colour contrast (WCAG 1.4.3) 1.4.3 Contrast (Minimum)
Add text alternatives to images (WCAG 1.1.1) 1.1.1 Non-text Content
Give links a discernible name (WCAG 2.4.4) 2.4.4 Link Purpose / 4.1.2 Name, Role, Value
Give buttons a discernible name (WCAG 4.1.2) 4.1.2 Name, Role, Value

These guides cover automated checks (~30–40% of WCAG criteria). A full audit also needs manual review.